Recently, with reductions in size, weight, and power consumption in electronic devices and increases in battery capacities, the number of battery-driven electronic devices is increasing. Further, close-range data communication between devices is also prevailing as a form of utilization. The same goes for electric power in connection with these situations, and close-range power supply technology is drawing attention.
For example, as described in Japanese Unexamined Patent Application Publication No. 2008-206327, a conventional contactless charging system is composed of a power transmitter unit in which a primary side coil is included in a charging table or the like and a mobile electronic device including a secondary coil and a rechargeable battery, and a user places the mobile electronic device on the power transmitter unit. This forms electromagnetic induction coupling (magnetic field coupling) between the primary side coil of the power transmitter unit and the secondary side coil of the mobile electronic device, and electric power is supplied to a charging device side, thereby charging a secondary battery.